retake your tests as you should not have 0 nitrate then post the real results. as for PH why in the world would you want to drop to 4 that will just make things worse your ph seems just fine.
as for your ray some people say this happens with rays that are not eating but could be something else. tell us everything about your tank like tankmates, wc schedule, what are you feeding and how often, what are you treating your water with, lighting, and things of that sort.